The persistent deposition of high levels of nitrogen (N) affects the decomposition of litter in terrestrial ecosystems. Despite their essential roles in microbe-mediated litter decomposition, the responses of extracellular enzyme activities (EEAs) to N deposition and their regulatory functions in litter decomposition remain poorly understood. Here, we conducted a meta-analysis based on 585 paired observations retrieved from 42 studies to assess the responses of litter EEAs to N addition and determine their contributions to litter mass loss. The results demonstrated that N addition enhanced the enzymatic activities of β-1,4-glucosidase (BG), β-1,4-xylosidase (BX), cellobiohydrolase (CBH), invertase (INV), leucine amino peptidase (LAP), β-1,4-N-acetyl-glucosaminidase (NAG), and acid phosphatase (AP), while suppressing the activity of phenol oxidase (PO) in litter. The effects of N supplementation on the activities of BG, CBH, NAG, AP, and PO generally decreased as litter decomposition progressed. The changes in the activities of litter cellulase and ligninase following N addition collectively explained 70% of the constrained variance in mass loss responses, with their effects varying across different stages of decomposition. Litter mass loss was enhanced by N addition within the first year of decomposition, but suppressed beyond 1 year, and these effects positively correlated with the responses of litter cellulase and ligninase activities during the respective periods. This suggests that the increase in litter mass loss during early decomposition was primarily driven by an increase in cellulase activity induced by N addition, while the reduction in mass loss during prolonged decomposition was regulated by the N-induced suppression of ligninase activity. The study identifies the responses of litter EEAs and their regulatory roles in decomposition following N addition, highlighting the significance of incorporating litter enzyme parameters into ecosystem models to enhance predictions of carbon cycling.